Optical device for an endoscope with bellows expansion compensation means

ABSTRACT

An optical device for an endoscope comprises inner and outer tubes of which the inner contains the optical system, a sleeve of wider internal diameter than the tubes, the sleeve being rigidly connected to the proximal end part of the outer tube and being connected to the inner tube, and means interposed in the connection between the inner tube and the sleeve for taking up relative longitudinal expansion therebetween.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an optical device for medical endoscopes ortechnical (engineering) endoscopes e.g. for examining visually theinside of an object such as a car engine, and more particularly to suchan optical device of the kind comprising an inner tube which holds theoptical system and is situated in an outer tube, the outer tube beingrigidly connected at its proximal end part to a sleeve of enlargedinternal diameter which is connected to an eyepiece and through whichthe inner tube passes.

2. Description of the Prior Art

In the known optical devices of the aforementioned kind of endoscopes,on the one hand the outer tube is rigidly connected to the distal partof the wide sleeve and on the other hand the inner tube is rigidlyconnected to the proximal part of the wide sleeve, e.g. by soldering.However, if for medical reasons sterilisation with superheated steam at134° C has to be performed or, in the case of engineering endoscopes, ifthey have for example to be inserted through sparking-plug holes inorder to examine the insides of the cylinders of engines while they arestill hot, differing amounts of expansion occur between the widenedsleeve connected to the outer tube and the inner tube, which is alsorigidly connected to the sleeve. This difference in expansion sets upstresses which may give rise to fractures, particularly at the solderedjoints.

The main object of the present invention is, therefore, to compensatefor the difference in expansion of the metal parts of the opticaldevice.

SUMMARY OF THE INVENTION

This object is achieved in accordance with the invention in an opticaldevice of the kind initially described, be freely enclosing the innertube, in the widened sleeve, in a member which takes up longitudinalexpansion and which is connected at its distal end to the inner tube andis provided at its proximal end with an extension which is a clearancefit around the inner tube and is rigidly connected to the proximal partof the widened sleeve.

In this way it is possible for the widened sleeve, and the eyepiece, toexpand freely relative to the inner tube which passes through it, bywhich means stresses, and the risk of fracture which they involve, areprevented, in particular at the soldered joints.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial section through a known optical device for endoscopeswith the distal part of the device being shown in side-view, and

FIG. 2 is a similar axial section through an optical device constructedin accordance with the invention.

In the drawings the same reference characters are used to designate thesame or similar parts.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, an endoscopic optical device consists of a metalinner tube 1 which contains in a known way the optical system (i.e.lenses, dimming rings and so on for image transmission) (not shown) andwhich extends into a metal outer tube 2. The space between the inner andouter tubes 1 and 2 is used to accommodate a fibre light conductor 3which encloses the inner tube at its centre to provide straight-aheadvision and eccentrically to provide lateral vision, so doing in acrescent shape. Alternatively, the space between the inner tube 1 andthe outer tube 2 may be used to house electrical conductors which leadto a lamp at the distal end of the device. In the case of the opticaldevice shown, the fibre light-conductor 3 is curved sideways out of thespace between the tubes 1 and 2 into a metal sleeve 4 which is widerthan the tube 2 and thence to a nipple 5 to which a light conductor froma light source can be connected. The fibres of the light-conductor arecemented into the nipple 5 and are ground flush with the latter at itsouter end.

The proximal end part of the outer tube 2 is soldered at 6 to a flangedcollar 4a associated with the sleeve 4, and the proximal part of theinner tube 1 is soldered at 7 into a flanged collar 4b at 7 having anexternally threaded projection 4c. An eyepiece section 8, which has atransparent terminal disc 9 conveniently made of glass, is screwed ontothe threaded projection 4c, and an eyepiece 10 itself is screwed ontothe eyepiece section 8 by means of interengaging screw-threads. Theoptical device of FIG. 1 has the disadvantage that the soldered togethermetal parts 1, 2, 4 undergo different amounts of expansion, for examplewhen heat sterilized, so that stresses and fractures may result.

FIG. 2 shows an optical device which is constructed to compensate forthe differing longitudinal expansions in the soldered-together metalparts, 1, 2, 4 when being heat sterilized, thereby to substantiallyreduce or eliminate the stresses and fractures which may result in thedevice of FIG. 1. In FIG. 2 a bellows 11 is interposed between the innertube and the distal end of the bellows 11 is soldered at 12 to the innertube 1 in the sleeve 4, the bellows being provided at its proximal endwith a cylindrical extension 13. This extension is a clearance fitaround the inner tube 1 and is soldered at its proximal end, at 14, tothe projection 4c of the flanged collar 4b.

Should differing amounts of expansion now occur in the widened sleeve 4connected to the outer tube 2 and the inner tube 1 when heatsterilisation is taking place or when articles are being examined athigh temperatures, the difference in expansion is taken up by thebellows 11 whereby internal stresses are compensated for and thepossibility of fracture is eliminated.

Various modifications may be made without departing from the scope ofthe invention as defined in the appended claims. Thus any othercomponents which take up expansion may be used instead of a bellows,e.g. telescopic tubes, elastic sleeves or the like.

I claim:
 1. In an optical device for an endoscope, comprising an innertube which holds an optical system and which extends into an outer tubehaving a proximal end region rigidly connected to a sleeve which is ofenlarged internal diameter, said sleeve being connected to an eyepieceinto which the inner tube also extends, the improvement comprising:means interposed between the inner tube and the sleeve for taking uprelative longitudinal expansion therebetween, whereby to compensate fordiffering amounts of longitudinal expansion in the inner tube, the outertube and the sleeve to reduce the possibility of stresses and fractureswhen the optical device is heated; said means comprising a bellows whichextends around said inner tube, said bellows being connected at itsdistal end to the inner tube and being provided at its proximal end withan extension which has a clearance fit around the inner tube and isrigidly connected to a proximal part of the sleeve.